Hot-fillable plastic containers are designed for the packaging of liquids (e.g., juice) which must be placed in the container while hot to provide for adequate sterilization. During filling, the container is subjected to elevated temperatures on the order of 180.degree.-185.degree. F. (the product temperature) and positive internal pressures on the order of 2-5 psi (the filling line pressure). The container is then capped and as the product cools a negative internal pressure is formed in the sealed container.
Biaxially-oriented polyethylene terephthalate (PET) beverage bottles have been designed to receive a hot-fill product with a minimum of thermal shrinkage and distortion. Such a bottle is described in U.S. Pat. No. 4,863,046 entitled "Hot Fill Container," which issued Sep. 5, 1989 to Collette et al. The Collette et al. container is provided with a plurality of recessed vacuum panels in the middle panel section of the container, which reduce the magnitude of the vacuum generated in the filled and capped container to prevent any large uncontrolled shape distortion. As the product cools, the vacuum panels (all of them) deform and move inwardly in unison. A wrap-around label covers the vacuum panels and is supported by raised central wall portions in the vacuum panels, post areas between the vacuum panels, and horizontal glue land areas above and below the vacuum panels. Vertical recessed ribs may be provided in the post areas and within the vacuum panels to increase the longitudinal stiffness of the panel section.
The design of the vacuum panels may vary; other designs are illustrated in: 1) Design U.S. Pat. No. 315,869, "Container Body For Liquids Or The Like," Apr. 2, 1991 to Collette; 2) U.S. Pat. No. 5,255,889, "Modular Mold," Oct. 26, 1993 to Collette et al.; 3) U.S. Pat. No. 5,178,289, "Panel Design For A Hot-Fillable Container," Jan. 12, 1993 to Krishnakumar et al.; and 4) U.S. Pat. No. 5,303,834, "Squeezable Container Resistant To Denting," Apr. 19, 1994 to Krishnakumar et al., each of which is hereby incorporated by reference in its entirety.
There are numerous plastic containers with end grips for cold-fill applications. For example, three patents recently issued to Ota et al., U.S. Pat. Nos. 4,890,752, 4,993,565, and 5,199,587, all directed to blow-molded PET containers with an end grip. The Ota containers are designed to provide sufficient mechanical strength to resist crushing during drop impact and/or the increased pressure caused by gripping of the container. However, there is no mention of the use of these containers for hot-fill products, and the containers do not include vacuum panels.
One prior art attempt to design a hot-fill container with an end grip is described in U.S. Pat. No. 5,141,121 to Brown et al.; however, the Brown container is not known to have been commercialized. Brown describes a grip within a vacuum collapse panel, but the design of the Brown grip/panel is believed to be deficient. More specifically, the Brown grip/panel is formed (blow-molded) in an outwardly bulged configuration, and is intended to collapse inwardly to alleviate the drop in pressure during cooling of the product (see Brown FIG. 3). However, it is believed that the negative pressure generated during product cooling is not sufficiently strong to pull in the outwardly bulged panel section. Thus, Brown does not solve the problem of providing a hot-fillable container with an end grip.
Another apparent attempt to provide a hot-fillable container with an end grip is shown in Design U.S. Pat. No. 334,457 to Prevot et al. The Prevot container has recently been commercialized (Welch's.TM. grape juice). The container is molded with a cylindrical panel shape (see Prevot FIG. 7), but during hot-filling, sealing and product cooling apparently undergoes a deliberate or unintentional transformation to become an ovalized or egg-shaped container. The commercial container is highly ovalized. The present inventors believe this ovalization is due to the absence of flexible vacuum panel sections which can move inwardly to lower the internal vacuum. The ovalization is undesirable in terms of the container's stackability and packability in a shipping carton and on the retail shelf. Thus, the ovalized Prevot container fails to provide a satisfactory solution.
Thus, there is a need for a hot-fillable plastic container having a panel section with readily deformable vacuum panels and an end grip, and which panel section resists ovalization and other forms of deformation during hot-filling, cooling, drop impact, and handling.